Per-capita claims rates for decompression sickness among insured Divers Alert Network members.

Decompression sickness (DCS) in recreational diving is a rare and usually self-limiting injury, but permanent disability can occur. Incidence rate estimates are difficult to establish because the number of divers at risk is usually unknown in population samples with well-documented DCS. We estimated the annual per-capita DCS incidence rates for 2000-2007 based on insurance claims submitted by members of the Divers Alert Network (DAN), Durham, N.C., with dive accident insurance. The overall per-capita DCS claims rate (DCR) was 20.5 per 10,000 member-years. Based on the age-adjusted DCR, males submitted 28% more claims than females. Male-to-female difference was greatest between 35 and 40 years of age and disappeared by the mid-50s. Highest rates were observed in the 30- to 39-year age category, after which DCR declined with increasing age. Highest yearly DCR was estimated in 2002. Insurance dropout rate was greater among those who had DCS in the first year of their insurance compared to those who did not have DCS in their first year.

Scuba injury death rate among insured DAN members.

We calculated the annual rates of diving-related deaths among DAN-insured members in the period from 2000 to 2006 and investigated the effects of age and sex on death rate by logistic regression. We determined relative risks for divers < 50 and ≥ 50 years of age for drowning, arterial gas embolism, and cardiac incidents, the three most common disabling injuries associated with diving death. There were 1,141,367 insured member-years and 187 diving-related deaths. Males made up 64% of the members. Individuals ≥ 50 years of age constituted 31% of the fatalities. Insured mean age increased from 40 ± 12 to 43 ± 13 years over the seven-year study period. Annual fatality rates varied between 12.1 and 22.9 (average 16.4, 95% confidence intervals 14.2, 18.9) per 100,000 persons insured. The relative risk for male divers in their thirties was six times greater than the risk for female divers in the same age range. Fatality rates increased with age for both sexes, but the higher relative risk for males progressively decreased until the rates became similar for both sexes after age 60. Death associated with cardiac incidents was 12.9 times more likely in divers ≥ 50 years of age. We recommend that older divers adjust their participation in diving according to health status and physical fitness, maintain fitness with regular exercise, and abstain from diving in conditions likely to require unaccustomed physical activity.

Estimating ecological thresholds for phosphorus in the Everglades.

The Florida Everglades, a wetland of international importance, has been undergoing a significant shift in its native flora and fauna due to excessive total phosphorus (TP) loadings (an average of 147 t per annum from 1995to 2004) and an elevated mean TP concentration (69 microg L(-1) of TP in 2004) from agricultural runoff and Lake Okeechobee outflow despite the use of 16000 ha of stormwater treatment areas. Here, we present a Bayesian changepoint analysis of long-term experimental research and show that exceeding a surface water geometric mean TP threshold concentration of 15 microg L(-1) causes an ecological imbalance in algal, macrophyte, and macroinvertebrate assemblages as well as slough community structure. A phosphorus threshold for all trophic levels may be more realistic and protective when presented as a threshold zone (12-15 microg L(-1)) because estimates of uncertainty must be utilized to accurately define TP thresholds, which change with seasons and water depths. Most interior areas of the Everglades are currently at or below this threshold zone, but the exterior areas near inflow structures (except for the Everglades National Park) are presently receiving double or triple the proposed threshold. Our Bayesian approach, used hereto address ecological imbalance along nutrient gradients, is applicable to determining thresholds and stable states in other aquatic ecosystems.